Degradation picks are known to be used in such fields as road milling, mining and trenching to engage and degrade tough materials such as asphalt, concrete and rock. Such degradation picks may be secured to an exterior of a movable support such as a rotatable drum or continuous chain so as to be repeatedly brought into contact with a surface of a material to be degraded. Each degradation pick may comprise a hardened tip disposed on a distal end thereof and designed for repeated impact with a tough material. Such repeated impact may break up the tough material into aggregate pieces. To secure such degradation picks to the movable support, a generally cylindrical shank opposite the hardened tip may be disposed within a bore within a block that is rigidly fixed to the movable support.
As this repeated contact may cause significant wear, it may be desirable to increase the number of degradation picks in an operation to reduce the wear on each individual degradation pick and, consequently, extend its functional life. It may be especially desirable to position additional degradation picks in strategic locations around the movable support where wear is likely to occur. For example, the edge of a rotatable drum when viewed along a rotational axis thereof may engage tough materials not only around a perimeter of the drum but also beyond the edge of the drum. In such cases, it may be desirable to position additional degradation picks proximate the edge of the drum to engage this additional material. Traditional blocks, however, comprise a given footprint requiring a certain amount of space on the exterior surface of the movable support thus limiting the tightness of any degradation pick placement.
For example, degradation picks may be disposed proximate an edge of a rotatable drum by attaching a ring to an end of the drum to hold additional degradation pick blocks. For instance, U.S. Pat. No. 4,225,190 to Hoffmann describes a mining auger which is used in the underground mining of coal comprising an end ring along its outer periphery. A plurality of tool holders is provided along a free edge of the end ring. The longitudinal axis of each tool holder coincides with the longitudinal axis of each cutting tool bit arranged in the respective tool holder.
By way of another example, U.S. Pat. No. 4,411,475 to Best et al. describes a cutting drum for an extracting machine assembled of a base body having a frustoconical configuration and an end ring which is detachably mounted to a major end face of the base body. The end ring is provided along its periphery with a plurality of tool holders for accommodating picks.
Despite these advancements in the art, the need for even tighter formations of degradation picks than those possible by arranging tool holders around the periphery of an end ring is still desirable.